Field of the Invention
The present invention relates to a planetary reduction gear device suited for a case in which the outer diameter of a planetary reduction gear device is restricted and at the same time a high torque capacity thereof is required.
Description of the Related Art
The inventor of the present invention proposes a small backlash planetary gear device in JP 2002-031196 A. In this device, there are provided two carrier plates for supporting planetary shafts that support planetary gears on both sides. The carrier plates are rotated relative with each other, whereby adjusting backlashes
It is typically adopted to widen tooth width of the gears constituting a planetary gear device in a case in which a high torque capacity of the device is required under such a condition that the outer diameter thereof is restricted. However, there is a limit to increase the tooth width, and the torque capacity cannot be increased further more after the tooth width is increased to exceed a certain width. This is because widening of the tooth width makes a tooth-trace load distribution uneven, and it also makes the planetary shafts longer to decrease the strength thereof.